Elemental or isotopic analysis by mass spectrometry is known to be subject to interference from polyatomic and doubly charged ions. Interference arises when an ion has a mass-to-charge ratio that, within the limits of resolution of a mass spectrometer being used, is the same as that of an isotope of analytical interest. Such interferences can compromise the detection limits and dynamic range of the analysis, and can be particularly troublesome when an element of interest has but one isotope. It is known that an inductively coupled plasma (ICP) ion source is capable of generating many oxide, hydroxide, and doubly charged ion interferences. Other types of sources for atomising and ionizing a sample for elemental analysis by mass spectrometry such as for example Microwave Induced Plasmas, Laser Induced Plasmas, and Glow Discharges also produce interfering ions.
An object of the present invention is to provide an apparatus and method for mass spectrometry in which such polyatomic and doubly charged ion interferences are attenuated.